kate is right...portable is relative.
i've had a "long bed" mini-brute for years. it will sew 3 layers of 5-6 oz. leather. but it is heavy.
the lightest thread i have tried is # 69, the heaviest #135, usually use #92 .
if i had it to do over, i would pick the sailrite with a monster wheel and solid state foot control. though that is much more expensive.
the leather presser foot is just a regular foot with grooves ground off.
if you do choose one of these machines for public displays, search around for the portable setups that yachters use to sew their sails while afloat. some are pretty clever.
as a last thought, except for bagwork most leatherworker doing harness and holster work don't seem to like these machine. that said, i've been in a couple of car upholstery shops that used either the mini-brute or the sailrite and a canvasworker in wyoming with a thompson.