Resoling Birkenstocks with leather

I have been on the look out for a pair of slippers with cork midsole - I thought I had found the perfect pair with a pair of Haflinger wool clogs.

To my dismay they have fallen a part rather quickly. Instead of continuing my search I’ve resolved to resole a pair of Birkenstock Bostons with leather soles.

My question to you all - what type of leather would be best suited for this purpose and are there recommended vendors.