Congratulations on your new-to-you PT908 and Welcome to this forum!
PT92 grips will NOT fit a PT908, as they are substantially different handguns.
The PT908 is Compact Browning/Sig Short Recoil Design, with an 8 round magazine capacity. The PT92 is a Full Sized Service Pistol, using the Walther P38/Mauser Oscillating Wedge Locking System, with a 17 round magazine capacity. Hence, the PT92 grip is substantially larger.
I have both a PT92 and a PT908. Wonderful handguns, both!