If you truly can’t find objective, third-party data on the size of your market … then do a bottoms-up analysis instead. You should be doing this anyway.
E.g.,
There are 500,000 businesses that could use our new / novel product (because …)
x
$30/month (which is a comp because of comps A, B and C)
=
$180,000,000 initial market size.
