There are a few variants of bridges that can be suitable for fiddles with sympathetic strings
I have used baroque bridges from milostamm.com.
Both the variant BT where the sympathetic strings have been placed just above the feet of the bridge
and the variant BB where the sympathetic strings have been placed higher up on the bridge
Some people use bridges for hardanger fiddles to Swedish violins with sympathetic strings. I have no experience of them and don't know if they can be bought semi finished.