A late 90s Geo Prizm or 92-01 Corolla (probably the same as the 89) works fine. Toss the bracket that it comes with and swap the actuator lever. The valve then screws onto onto the stock bracket just like the old one. Hose ports are slightly larger but they fit no problem. Btw, neither it nor the stock valve completely shuts off flow through the core when closed. That would be a bad thing.
Another option is the generic heater valve from older GM cars. For example:
http://tinyurl.com/3mp22a
An "upgrade" in the sense they fit, are metal, and will allow you to get rid of the stock vacuum actuator. These types of valves are normally open and close with vacuum. That's opposite how the stock valve works but very easily corrected. So easy that if you can't figure out how you shouldn't try using it.
There are lots of other options out there if you're willing to use a straight valve. Otherwise stick with the Geo/Corolla one. It's as close to original as you can get without buying a whole new assembly. Even earlier Toyota valves are metal but will require a lot more modification.
As noted you could simply delete the valve altogether (connect the hoses) but doing so will cost you around 10 F in AC temps. Shouldn't be be an issue for young overly testosteroned owners who think AC is for pussies...
