I would choose something:

• small
• completely different from the K1000

Something small, because unless you really like heaving heaving things around, you already have one reasonably bulky camera to deal with, and the additional camera you're most likely to use in such circumstances is one that's physically easy for you to manage.

Although you asked for advice on "a second body", unless that is also a Pentax K body, you'll now be dealing with two systems of bodies and lenses. That's not really the way I'd like to travel.

So, I'd suggest to consider something with a fixed lens, rather than a body (and new lenses, if you're not getting a K-mount body).

Something different, because you might as well give yourself as many options and open as many opportunities as possible, rather than overlap.

Something different from an SLR will allow/require you to think and see in different ways, make it possible to do things you couldn't do with the SLR, use it when you couldn't use the K1000, and so on.

On that basis, my suggestion would be a pocket-sized rangefinder, such as an Olympus XA, a Canonet QLIII 17 or a Ricoh 500G.

Armed with something like that and your K1000, you'd have a pair of pleasant-to-use cameras, that between them wouldn't be too cumbersome to carry around, and represent quite different ways of photographing.

Which small rangefinder?

I think it's easier to find a Ricoh 500G in good condition than a Canonet cheaply, but in either case you should check whether you're going to have to replace light seals.

You can spend a bit more and buy an XA - and that would be my choice, just because it's that much smaller and easier to carry.