So after some research, turns out the Street 750 grips are odd.

7/8 bars, but 1 1/8 throttle body tube. They are 4.5" (115 mm) long too, closed end.

Turns out a 1 1/8" throttle body diameter is commonly used for 1" bars, and the left grip is padded thick, to give us grips that feel like 1" bars, I guess they wanted it to feel like other Harleys, but with 7/8" bars underneath.

So I got this idea from another post, and will try it out soon:

Use high-temperature automotive electrical tape to wrap the left bar, expanding it to approx 1". Then any heated grips made for cruiser 1" bars will work.

Look up Heat Demons. I ran a set on my last bike. You remove the grips and the elements stick to the bars and you slide the original grips over them. They make various kits from a simple high low to a push button 5 level heat kit. I had only one issue and they warrantied them fast as the switch was in the ground circuit if the element shorted to the bar it would heat up but now they include shrink tube for the clutch side so the hear stays in the grip and won't accidentally short to the bar.

Heat grips are not that great. Heated Gloves work much better.

Agreed on the heated gloves, that's what I run.

Only thing is -- some heated gloves don't bother heating the palm, because they figure that your heated grips have that already covered...

My Heat Demons on 2 with my normal set of leather gloves would almost cook you hands, I couldn't hold them on high..LOL New owner sure loves them. How are you hooking in to the bike for the gloves? I was reading these have a fairly weak charging system to add too much accessories.