A snap-on forend on a slinged TC, pistol or carbine, would mean using a barrel clamp sling stud. Not a choice I'd ever take on any firearm.
Any machinist could make knurled attaching bolts for you and they wouldn't cost much. Flush mounting may be possible depending on the thickness of your forend and the bolts head size, but also would require the forend to be hogged out large enough around the bolt head to facilitate getting your fingers on it. Would be a pretty big bevel for most adult fingers, and of course weaken the attachment due to less left in forend thickness under the bolt to purchase on. No different than a recessed sling stud, but they are usually down in brass inserts to help the strength of the forend wood they replace.
Unfortunately the three gents I had make most of my personally designed accessories for my TC's and other firearms are no longer doing custom work, one on the east and two on the west coasts. All were long time TC users, so did an excellent job following just verbal descriptions of what I wanted. And as old friends and hunting pards they did them more often than not as gifts. So I didn't ask for royalties if them produced more for others.

I'm sure Steve Stratton would make them for you if you want them from someone who makes and sells other TC accessories. A search will find his website - he's in Hurricane, UT. They could even doube as the sling stud if made to do so if wanted.
Luck with whatever you do.