I had always used https://mysignature.io/ - but that was only because it was the first one I found on Google. I never had any issues for some pretty basic ones, but I'm not a designer, and was doing it for cheap bosses I was working for.
With my current business, our in-house designers sorted it out for us, and it didn't seem like a big task at all. You might be able to find someone on Upwork or Freeeup.com to do some cheap freelancer work. Then installing it on your email client will be included in their FAQ or support pages :)
Hope that helps!