Looking for a good tent peg hammer; non-rusting, durable, slim to pack....

This may be the solution, available with weights of 150 to 250 gram, some with Teflon-faced heads and various styles of head and handle.

I went for the simplest 'Williger' style. These are 'Bone Mallets' and sell on eBay for between £10 and £20!

Bone Mallet