Liquivision X1 -- by far the best choice for size and readability, very flexible, out of your price range. Liquivision Xen/Xeo -- very nice size, very readable. I don't know what the Xeo is running, or what the asking price for the new, recreational Lynx will be, but probably comparable to the D9. I have seen the D9, and it is comparable in size to the Mosquito (a bit bigger) but not very readable.
I had not considered a Liquivision computer, but honestly the Lynx seems about perfect! It is in the budget, looks small enough, and seems like it would be easy to read. How do the transmitters work with this computer? It says on Liquivision's website that they will be available this spring.