Vic, take it from a P-38 freak. Bigger electric 3 blades in a counter rotating version are few and far between, other then custom like a Vario, brand.
Or do like I do. Find a close prop with the right pitch and cut em down. And often it's a gas prop. I use the APC 15 x13 x3 all the time and cut it down to say a 14 to keep the amps in check.
You are only removing 1/2" off the tips and I've never had a problem. Just balance it afterwords.
And yes before I get jumped on, you are changing the way the prop performs but it's so small of a change you aren't going to notice it.
And I'm sure you know, a tractor blade mounted on a rear is a pusher. All you do is change the motor rotation to make it work.
Biggest thing why you don't see em is other then looks, on r/c they don't tend to have the influence on a craft like a full scale one does.