Are you adding a 129 dish to an existing setup? Are you looking for a Western Arc setup with 110/119/129? If just a single satellite location a Dish Pro single or dual LNB would be appropriate, if you are going to add it to other satellite locations you will need a switch.
Agree, the Dish 500 is not completely round, I think it's 20x22. But in any event, I had 2 Dish 500s, back in 2007-2009 before eastern arc, With one at the 61.5, and the other 110/119. And it worked fine.
Any Dish with a single LNB is going to work. The arm is designed to work with the reflector at dead center when zero out.
The LNBS and Skew are what makes the multiple orbital locations possible from a single dish.
You can point a 1000.2 at any one orbital location and it's the same as taking an 18 inch round dish. Only issues, They probably don't make an adapter to have only a single LNB on the 1000.2 or .4 dishes.