I found these recommendations on the Midwestern Doctor substack, near the end of this article - https://www.midwesterndoctor.com/p/dmso-is-a-miraculous-therapy-for - and it is possible this part of the article is behind a paywall so I include the info here.

That site recommends three brands.

•Jacob Lab (e.g., this gel or this liquid)—which is 99.98% pure.

from jacoblab.com - this is the highest recommended, but also the most expensive.

•Nature’s Gift (e.g., this gel or this liquid)—which is 99.9% pure.

the brand Nature's Gift is available on amazon.

Nature's gift also makes a gel which is 70% DMSO, 30% aloe.

•The DMSO store (e.g., this gel or this liquid)—which is 99.995% pure.

this brand, DMSO store, is also available on amazon