Does the skillet have a waffle base?
Most if not all the KR frypan styles have this. If so you don’t really need a trivet for it. The KR is so efficient that enough moisture sits in the dimples for most uses.
If you bought it as a set though, I assume the 5L is a stockpot style. Albeit small. You will probably want one in that but you should have enough height there to use one of the petal type fold up steamer baskets.
I measured my KR trivet, and it 23cm across. It came with the hotel series though which is 28cm across. I sometimes use it in my 24cm 2.5L frypan style, but it will be too big for yours.
Another thought is to visit an Indian (Asian not American) provision store. My local one has several low metal trays that make good trivets. I have one with removable feet that would do your job nicely.