Not sure if there is anything as good as karma cannon since the other benefit of it is it's good target for rollback but here is some option that maybe work: card with flip face down effect -> book of eclipse but it can't out link monster and give tons of draw at end phase. Other option is floodgate trap hole but can only be activated when your opponent summon a monster and it still can't out a link monster. card that disrupt lots of cards like karma cannon -> torrential tribute but it can destory your monster too.

The big role for this deck it serves is a normal trap that "clears" the opponents board, while there are alternatives it is largely considered the best one since it flips to stop floats, gets rid of links and unaffected monsters, and doesn't destroy your own monsters

The notable cheaper options are

Weighbridge (which i also play), Needle Ceiling, and Torrential Tribute

That is probably true (or at least a 2-of) but it is a UR, and didn't want to craft it. Cambroaster is actually pretty good, even thought about playing 2. It is one of the few-in-archetype ways to deal with backrow, it lets you search a paleo if the xyz gets impermed, and it helps get rollback in grave when you draw it

Besides being awesome, it is really good against stun/branded/backrow decks to clear out their spell traps (I tried heavy storm duster but wasn't impactful enough for rollback and it only hit backrow if you drew it anyway)