I agree the replacement doesn't sound expensive at all. If it's not a gaping hole in the inner tube, go ahead and patch it and keep it as a spare for later use.

I believe Schwalbe make several Marathon variants in the 20 inch size. If you are particularly interested in puncture protection the Marathon Plus is second to none. It's also a heavy and expensive tyre, but very durable. Many of the Marathon models have the reflective strip too. Lah!

www.schwalbe.de

--J