Again, if it were me, I would get a little deal from the dollar per gallon sale at one of the box stores.
For a brand new tank that way after cleaning you can be sure no one used copper or other bad things in them. I would always test the tank with a couple Cherry shrimp culls as well (to make sure there hasn't been pesticides sprayed in the store or factory or tanker or whatever).
If they have a 15T that would be good or a 29G long (you don't really need on that big a 10 would also work, but if you got lots of shrimp breeding you might need a little more room as well as more room to accomodate tank errors), but I would use a glass tank so you can visually observe the growth, progress and any problems begin so you could fix them.
Watching the tank is critical if you don't already have experience with these more delicate and difficult to keep higher quality creatures.
Check out the PRL (Pure Red Line) on ebay.
Also consider one of the substrates that help lower the pH in the tank. They do leech ammonia and need to be set up running for a number of weeks probably 6 weeks, could be more. I am planning a PRL (maybe just nice CRS) tank in the fall/winter (swamped & too busy now). Make sure to post a link for your build thread here so I can follow how yours goes.