If you can get over the "ick" factor, pick up a piece of rag from the side of the road to wipe the chain. I passed a recreational boating lake once on a weekend and I had my choice of nice clean towels that got left on top of something for the drive home.
With the dry lube I usually pack, I can go 4-500 miles in dry conditions, less in wet conditions, before it starts to squeak.
If my trip exceeds 3-4000 miles, I'll buy a new chain at shop when needed, or have a family member ship one to me along with maps, new clothing, brake pads, etc. Location may be a PO that takes General Delivery (call to be sure), a hotel in a town I plan on taking a rest day, a friend I plan to visit, or an agreeable Warmshowers host.