Suggestions for something on a PzII chassis?

That's a decent kit as well as their Marder II Ausf. D.

Tamiya makes a Marder II, but it's ancient. There are lots of PzII ausfs out there, but of course, most of them are tanks with different arangments of road wheels.

There are quite a few things you could build depending on how much modification and scratch building you want to do.

There were 12 15cm sIG auf Fhrgestell PzKpfw II (Sf) produced using a lengthened and widened Pz II hull.

There are several anti-tank guns mounted on the Pz II chassis. These include a 7.62 (SdKfz 132), a PaK 40/2 (SdKfz 131 Marder II), and the Feldhaubitze 18/2 (SdKfz 124 Wespe or Gerat 803).

You could also build the PzKpfw II mit Schwinnkorper, an amphibious tank used by the 18th Panzer Regiment in the central sector of Russia.

There was also a bridgelayer, a pioneer version, and two vehicles with a PaK 38 installed.

There are quite a few choices...