I believe the Surface 604 does.I never gave it much thought as my middrive has a throttle (iZip).
It is suppose to cut off at 20mph, I would guess that any production bike would be the same.
If you cannot source one, check out Luna, or any of those companies that build bafang mid drive bikes.
You build ebikesI'm delivering a bike to a friend that I finished, it has a throttle, a Bafang mid-drive and an ERT controller. Makes over 3000 watts and does 45mph, with proper ramping programmed in, it's as gentle as a kitten. Or as wild as a tiger! I wouldn't have an ebike without a throttle or with a 20mph limit! Most cars do well over the posted speed on any road. The limit is common sense. Ebikes should be the same. This bike won't be driven at top speed, but when a really big hill, a heavy load or an unsafe situation demands it, it will be able to deal with it, and have power to spare, just like your car. If Europeans want to build weak, throttle less, 20mph Ebikes, let Europeans ride them! Americans like POWER! Just look at the forum pages that support the Bosch drive, people are constantly trying to 'hack' them to get more power. Why not just build Ebikes that have power and a throttle in the first place?!
Plenty. Biktrix with Bafang and Electra Townie with Bosch comes to mind. Luna has some, though it's been so badly bashed in a recent thread that I'm almost afraid to mention it ... Same Bafang motor as in Biktrix though. About the fact that throttle on Bafang mid-drive works only after 15 kmh - not sure, this is a controller and programming feature, nothing prevents it from starting from standstill.
Many production mid-drive bikes come from Europe, and throttles weren't allowed there. I heard that's changing in some places, but I haven't confirmed this. I believe there are production mid-drive bikes available here in the US, but I can't think of which off the top of my head.