The problem with the Pentax FA20 is that it is almost impossible to find in a workable condition.
I suspect most of them are really old (20-30 years?) and since most photographers dropped out of film some 10 years ago, these lenses have probably sat around for 10 years in cupboards etc, with mould growing on them.
When they come up on Ebay, they go for €300 or so for a mouldy one (which AFAIK cannot be fixed, at any price) and one recently sold for €800 or so. That is just a silly price unless you really want a small lightweight lens, but the K1 body is very heavy anyway so the benefit is IMHO wasted.
The other extreme is the current Pentax 15-30 zoom which is great for using the camera in a Taekwondo-style self defence
I was watching Ebay for the FA20 for ages and in the end got fed up with it. And in any case one is assuming the seller is honest
and understands what mould looks like.
The Zeiss is very expensive but the size and weight are good for the K1 body.