Perhaps this soldering grain would serve your needs? I have some and it is quite handy!
Position smaller parts in this fine reflective silicon carbide soldering grain. Odorless and re-usable, grain can be used wet (as a heat sink) or dry (to position parts). This product is designed for use with smaller, more delicate jobs; the force of a large torch flame will displace the material and interfere with its effectiveness. Non-contaminating; ideal for use with non-ferrous alloys. One package will fill a 7" annealing pan.
Catalog page: 2016-2017 Tools and Equipment Catalog p.476
This is a Rio Grande Exclusive.