The price of my current beam stopping material has gone through the roof. What are some other materials that have worked for some people in the past?

I am trying to weld L605 to HS-188, the weld joint geometry doesnt allow for a thick stopper, and copper sits too close to the joint and causes contamination. Molybdenum has shot through the roof in price in my area.

The parent material is also very pricey.

Any ideas?