I don't recall if a 17 mm will fit, I don't think so. The fit was fairly close. But if you have some calipers, you might measure it.
The key to making the stock Techmount stem work is that it has 3 grooves cut for 3 o-rings near the stem top, bottom, and center. The stock o-rings are a good fit, and I would not have a problem with them if I was not conservative about movement next to moving steering parts (ie, a bike without a damper there)
Try your local hardware store, once you get the 16 Techmount and compare the store's selection of o-ring diameters and thicknesses. You may have to put some rubber lube and use a bit of force to get the stem in. If you have a Dremel tool you could even take a sanding drum and tweak the hardware store o-rings until you get just the right fit. You have several options to tinker with if you too, want a tighter-than-stock fit.