Bill:
This is one deja-vu question! I asked about exactly the same thing about 1/2 year back on both T-L and Armorama! I, too want to detail a "kleiner" in the worst way! 
Ultimately, what I found out makes sad sense - there is, best I know, exactly one interior kit going for the interior of the Pz 1B command tank; the Verlinden kit made for the Italeri kit of this vehicle
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As both the Dragon and Italeri kits are 1/35, and of the same vehicle, the verlinden kit should fit OK. This kit will provide some key bits such as various chairs, radio set (but only one, I think), etc. It also provides the basic stuff on the floor - driver's station, tranny, battery box, drive-line and firewall, plus some other odds and ends.
In most ways, the Pz. 1B was, interior-wise, merely a slightly-stretched Pz.A- same firewall, most floor plates, drive train bits, driver's station, and most interior items. So, from this, there are some options: one could use the floor-level interior parts from one of those Dragon -1B variants (panzerjager, or that machine with the s.IG 33 on top). But that seems like too much sacrifice, to me!
Alternatively, a fine floor-level, vision-devices, etc., set-up can be made using the Tristar 1A or Dragon 1A interior and adding some length to the drive-shaft and some floor-plating...
The upper-level stuff can actually be pretty well scratched using the pics of interiors (such few as there are...) and looking at what the verlinden kit supplies up there. Or simply add in the Verlinden stuff and scratch in conduits and bits as you think go in.
I am thinking that I will use a Pz 1A interior from a Dragon or Tristar kit for the lower stuff, scratch in the upper bits (chair, voice-tubes, flag-rack, map table, etc.) using inteior pics as vague guides, and add in a stacked radio set from the Tristar Pz.38 or some other source which come with PE racks that can be doctored a bit. There are various kits where you have little chance of seeing a radio, yet radios and racks are provided... Natch, adding in power conduits, junction boxes, and head-phones seems to be a way to go!
Cheers!
Bob