there is a 10 ga forster slug, of course out of stock but cheap with 34 $ per 100 when available again
https://www.ballisticproducts.com/10ga-Rifled-HP-Lead-Slug-766gr-100_box/productinfo/RRLS766/

Diameter = .747"
Height = .1.051"
Weight = 766 grains (1-3/4 oz.)

maybe a little bit to small but you can patch it with paper or other stuff to the size you want. because its hollow you need real good nitro card wads betweenn bullet and powder.

here are teflon wraps 10 ga to 12 ga https://www.ballisticproducts.com/Teflon-Wraps-10-to-12ga-50_pack/productinfo/TEFLON/

maybe you can shot 12 ga bullets or slug in the 10 ga?