You may have already decided to buy the device that Mike suggested but if
you're looking for pH strips, Merck make them and I think they come in a
variety of ranges. If you do a search you should find a supplier fairly
easily.

Interesting that you mention the egg floating method as this was the method
used in the past to determine the strength of the lye solution for
soapmaking.

Vicki Younger
Redgum Soaps
Australia's first solar powered soapmaking facility
www.redgumsoaps.com.au