I have used Blackstone Labs. Google them. Also, lots of lubricant information on Bobistheoilguy.com. They can be found on BITOG also.
I just had an analysis done a month ago, $25.00 for the basic test, $10.00 additional for a more comprehensive battery of tests. I have had end of season tests done for the last two years.
This years test was more informational for the Amsoil performance as there was no residual conventional oil in the engine from the previous oil changes. As I said before, the oil tested out very well.
I see you are from CT so we may have similar experiences and conditions and you are a solo operator also.
Do you do snow removal? I am fortunate enough to be able to spend the winter in FL to avoid that. Also gives me time to check out the dealers down here, some of them are massive, can't believe the quantity and variety of equipment under one roof. One that I go to, the Stihl display alone is bigger than my dealers showroom, parts dept. and shop all together.