German self propelled guns

http://www.aviapress.com/viewonekit.htm?ALA-012

Bison II here

Tony Lee

Currently Tamiya is the only one who provides a Wespe, Alan is the only one who provides a Bison II (hard to find kit and will need work/help to build up depending), while DML has the Grille (both the H and M versions as tigerman points out) and Bison I covered. Alan also makes a Grille M and Bison I but both are very inferior to the respective DML kits. HTH!  

Tamiya's Wespe is a gem. I would recommend AM tracks, but they are not totally necessary.

Dragon makes a two Grilles, both in Smart Kit form. One is based off the Pz 38(t) H chassis with the gun forward and the other on the latter M chassis with the gun mounted towards the rear.

The Alan Bison isn't bad, just a basic kit though. Here is a review: http://www.perthmilitarymodelling.com/reviews/vehicles/alan/alan019.htm

tamiya makes a rather nice Wespe kit and dragon have a couple of Grille kits. I assume you mean 1/35th.

Alan models has the Bison II kit you are referring to.  The individual link tracks are a pain and it would be money well spent to buy a AM set. (5 mold stubs each to clean up) I believe the kit is a re-release and not common so locating one may be a challenge. I found Tony Lee one in Halifax, Nova Scotia a few months back, its gone now so he either had it mailed out or someone else bought it.