I have been doing my own photoetch for a couple of years now and i had the same problem as you.
I could not find any place to print in super small detail.
I ended up buying a Samsung C1810w laser printer.
I can not get detail as fine as 0.1 mm the smallest i have had succecs with is 0.2 mm.
But i think it would be very difficult to get 0.1 mm detail on DIY etch even with a perfectly professional printed mask.
Aligning the front and backside mask is very hard to do within a 0.1 mm tolerance.
Also i think you need super thin photoresist to achive such details.
I can send you a test print mask from the Samsung C1810 if you are interested.