The cheapest tiniest pump from Halfords will do just fine as you don't want the weight. If you can't get the tyre to seat on the rim and seal then run a ratchet strap around the circumference. Tighten it and it will squash the tread causing the beads to seat.
I have a fair amount of experience in this area. The eagle eyed will spot I run some Jeeps all with on board air system. The largest runs a 13cu ft belt driven compressor with 250psi 10l reservoir airtank . I can easily run airtools off road, but probably overkill for a Z4....lol