You must not be looking very hard. While the default for most online quoting systems is usually width/space of 6/6 mils I haven't found one yet that wasn't capable of 4/4 mils, at a significant price increase.
I haven't looked at your boards but according to the filename it's a board with a buck converter? Why could you possibly need that tight of spacing?
Assuming your board is relatively small, with 6/6 mil width/space you could get 10 made at a Chinese fab for about $5 USD + shipping. At 4/4 mil it will cost you about $75 + shipping.