According to pages 12 and 13 of the manual, switch "H" is the momentary and located on the right side of the TX.
If the switches are just plug in then just put it where you want, That would be the easiest, least expensive and fastest option. (But might void warranty)
Even if the switches are not plug in it should be a simple swap.

Is there a "Heli" version of this TX?

The location of the momentary switch and the ratchet on the throttle are the only differences between the airplane and heli versions of all of the other Futaba TX's.
The location of the momentary switch that you have is what has been on every Futaba "Heli" radio that I have owned. 8U, 9Z, 9C, 14MZ
I have never had an issue with the momentary on the right. it is operated with my pinky finger without affecting the stick.