They are super common to find. Here's the one I have on
Amazon:
https://www.amazon.com/Lees-Kritter...8&qid=1500225747&sr=8-3&keywords=critter+cage
I got the idea from wholesalers, when I would go there and walk around this is what they kept the octopus in. If it can keep octopus contained then it's pretty much good for anything. $300 is a fair price from a LFS honestly. I've seen them as high as $450 in LFS's. Typically your only going to get a lower price if you shop online or have someone in the local reef club that has a "source", IME there's always somebody that has a wholesale accounts in established reef clubs. They tend to be shy about it so they dont have a lot of people messaging them to use their account.
That's awesome that the LFS is offering that. I wouldn't worry about it either way. Eels tend to be very hardy as long as they dont end up on the floor, there are a few exceptions like the ribbon eel but the golden dwarf is pretty hardy IME. The only caveat I have found with them is that they tend to be picky eaters at first and sometimes wont take to certain foods at all that most other eels would happily eat. I use to try silver sides and krill and all that but most of the time my golden dwarfs wouldn't ever eat them. I just go to the local super market and buy wild shrimp (the kind you peel and eat) and I cut it up into bite size pieces and keep it frozen in some tuber ware with a shallow amount of water. I just pull it out and thaw it every time I feed and he's been happily eating this for 3 years now. It's much easier and cheaper then buying a bunch of aquarium specific food that he may or may not eat. I only get like 4-5 pieces of shrimp at a time and half the time the clerk just gives it to me for free.
If your newer to hobby its a good thing you learned your lesson about quarantining early. It's probably the single most important lesson I've learned in the hobby. I quarantine all fish for 4-6 weeks standard, except for mandarins due to their diet. I quarantine longer if something nasty pops up like ich or velvet. For almost all my fish except tangs I only dose prazi pro after they get accustomed to the QT, I dose twice 5 days apart. I only use copper or other meds if the fish in question present with symptoms. Tangs I copper no matter what since they tend to not be overly sensitive to copper unlike my wrasses, as long as you ramp up the copper dosage over time.
For the eel specifically i just dosed Prazi twice and then observed for the remainder of time. I QT for 4-6 weeks since I dont proactively dose medications unless symptoms show. The extended period of 4-6 weeks allows time for any nasties that may be hiding to pop up in a visible state where I can then treat. A lot of people have different methods with quarantining but I find this to work best for me. If you start coppering every fish you QT chances are your gonna cause some deaths as not all fish tolerate copper very well. And just so you know Eels is particular should not be exposed to copper unless it is absolutely confirmed that they are suffering from something such as ich or velvet. If I was going to copper a eel I would slowly ramp up the dosage over a 7-10 days and only raise the copper level to 0.3ppm which is the minimum level to effectively treat for ich. I would avoid this situation at all costs as eels do not fare well in copper. But basically just dose prazi pro twice, wait 4-5 days after the first dose then do a WC and then dose a second time making sure no carbon is being used during this process. from there its just observing and trying to get the eel to feed throughout its QT time.
I'm not saying my method is the best, as it is not 100% full proof but it works very well for me to where i have 22 very healthy fish for more then a year and have only lost 3 fish that all perished during QT and not in the DT. I would recommend checking out the disease and fish treatment thread here on R2R and educating yourself on how to QT and what to do if something pops up. From there you can make your own decision on how to QT. Also please read up on how to rid your tank of ich. If you had ich previously I would really research this to make sure your tank no longer carries the parasite.
I'll try to take a look to see if the ebay seller is still active. Hope all this helps!