https://www.amazon.com/Fluval-Chi-Aquarium-Kit-5-Gallon/dp/B003TM1BAE
Buy a 5 gallon tank like this. Get some gravel and some low maintenance plants (cryptocorynes and anubias). Just make the tank look as nice as possible. The nicer it looks, the higher your chances your boss will reimburse you and expense the cost of the tank.
There are cheaper tanks out there. You can make a pretty nice 5 gallon setup for less than $100. Making it in less than $100 seems like it could be reimbursed easily.
A few things.
They are expensive. About $60 on Amazon. For that much you can get a traditional tank that is 10 gallons which will make your fish happier.
They have a small footprint. Fish like swimming side to side rather than up and down.
The design of the tank means that it evaporates much more quickly than a traditional tank.
It's small size makes it unstable (as in the water parameters are more likely to change which isn't great for fish).
It's small size also means that an inexperienced aquarist can easily overstock it leading to poor water quality and a poor quality of life for the fish.
While this tank is aesthetically pleasing, I wouldn't put any fish in it. However, I think it can be made into a beautiful shrimp tank. Now obviously there are some fish that can live fine in there, but I just prefer to keep them in larger tanks.