Try the aquaspace 20L by Aqua One, nice size tank and I'm acutally considering it for my betta myself atm. Alternatively theres the Arcadia Arcs and Arc Pods you could look at. The Fluval Chi looks nice but I've heard bad stuff about it and I'm not sure about the open top with the shrimp (I don't really have any experience in them). As well as this, they're pretty pricey. If you didn't mind a little bigger, the 30L Aquastart 320 is usually a pretty good little tank from what I've heard. I'd definitely stay away from all BiOrbs if I were you - I can't stand mine and I am desperate to get rid of it! They really are shockingly bad tanks, especially with their high price tags. There are also the AquaCubes too as someone else said, though I personally find they can be pretty expensive. PaH had a nice little 15L that could have been great for you a while back and was a bargain at only £30 with pretty much everything you needed included, but as far as I know from going to my local PaH store, they no longer sell them. I know Practical Fishkeeping was giving them away to new subscribers so maybe it was just a limited time thing for that.