I was really disappointed by the selections I found at walmart, hobby lobby, JoAnn's & Michael's. Of those, I think the local Michael's had the best selection & I believe that's where I finally bought mine a few years ago. I think Target had a very long rectangular candle holder(think tiny 12 long) that I loved the dimensions of but the glass was so curved the entire "tank" would've been extremely distorted.
Every store I've seen with large decorative glass containers (ie potential fish bowls), they've always been really expensive imo... only places I've ever bought them have been garage sales and Goodwill.
Most places seem overpriced unless you spot them on clearance. Got a 2g cookie jar from Walmart for. $10, and a 2-3G bubble bowl from Michele's for more than I care to admit (was an impulse buy). Thrift stores are a good place to look, the ones by me never have anything or it's bought up before I go.
Walmart has 2-3g bowls for around $15-$20. Michael's has the same bowls for almost twice the price, but they also have smaller bowls and cylinders. Home Sense has some nice containers, some even with lids to keep out nosy cats. My favorite place is the local Sally Ann, Goodwill, Value Village, Thrift Shop, etc. I have found some old style goldfish bowls, a 2.5g vase, and some unusual things to add to my collection. Check out my bowls in the link.
I found an absolute beauty at HomeGoods yesterday. Granted, it was $24.99, which is at least $10 more than any of the other bowls/vases I bought there, but this one is huge. I estimate it will hold at least 5 gallons. The glass is a little thin (Polish Glass), but it is very clear and had only one tiny scuff and no bubbles. Working on planning my lighting, plants (need to be tall) and filtration now