Last time I had a chemistry set there was a vial of sulphur. If they really need it that bad they can buy a chemistry set.
https://www.amazon.com/Sulfur-Powder-12-Ounces-Consumption/dp/B0CNFY324V/ref=sr_1_10?crid=2CBUWLPHZ3FX&dib=eyJ2IjoiMSJ9.DH4gXptUSlZZ_hzDO3Xhan6j1rNILrhlcayTM7bcMutIwmL0STQeCCqo6G_vQSEMf_xpkdVVMgbKIgK65zQ61HFCGgfmra_XWtotuIGjtpO5COjPKr0TPjtb1uukARGbRo_cslPO6bmXGGzCnypUdIpd4W5ugTVDPMEQ3-hoXjp8F6Fm3ceQ297c2p0_trIJaBAXKajf5pMnvZxjPnfiDoRrt0CQEhjZvbtaf7v1UyvKzBgeSqOSB7YY0rpiYIlBgkZW0BmVlQyjG1gdlmAbAbjJINil6NuKegHev5Dtris.bU1eHG2MdVsMKUSC9WZp8cYN4rHOip9q0fAq1PySV8c&dib_tag=se&keywords=sulfur%2Bpowder&qid=1712421812&sprefix=Sulfur%2Caps%2C128&sr=8-10&th=1
50 lbs of sulfur available from Amazon. (And isn’t that an impressive link?)