Like you it's been years since I last purchased checks, I still have plenty of checks from my last order, because I rarely write checks. The last order that I made was back in 2017, and I purchase through my bank for convenience sake.
I see that you have received some well meaning advice to change your bank. (smile) I would not under any circumstances, switch my bank that I have been with for many years, and that I am comfortable doing business with just because they charge to order a box of checks from.
However, years ago when we all use to write checks for everything, I would purchase through the check companies that were advertised in the Sunday newspaper. I never had a problem with security.
I do not know this for a fact, but I personally believe that all of these companies pretty much go through a set number of printing companies, and the price varies depending upon the entity.
That's my two cents.