If your looking to scratch build, Achtung Panzer No. 3 has some excellent diagrams of the fittings for the shurzen. The best scale drawings of for the size, and shape of the shurzen that I have seen are in Panzer Tracts No. 4. Both of these books are good references for the Panzer IV.
Let me know and I can either photo copy the two pages and mail them to you, or scan and send you an email with the files attached.
However, these two books are great references, and if you plan on doing any more models of the Panzer IV in the future, I would highly suggest picking up a copy of each. Well…. At least Auchtung Panzer No. 3.
Good luck with your project.