I'm too lazy to look up the meaning of pine bark mulch fines, so would you mind telling me what it is?
pondy

not nuggets, not shredded. roughly 1/8" size.

I found some at a large plant place in the twin cities metro area a couple of years back - Gertens maybe?

FYI,
Many people here buy the purple bags of mulch from Wally World. They are 1/2-1" pine chips and work very well in potting formulas. Very cheap here.

1/2 -1 inch pieces are too large for potting mixes
looking for dust to 3/8 inch with highest concentration at
1/8 to 3/8

I find my pine bark fines at Petsmart..... they sell it under the name of repti-bark. It is expensive I think for the amount you actually buy, I got 48 quarts of the bark for 50 dollars, but I would pay that price for the product... it is clean, just the right size from the bag, and though not important for the mix, it smells amazing. Let me know what you decide, I too, am always looking for a new product to try...... I was going to try the stuff from wally world until I heard that using partially composted materials would be bad for the mix......

Keep me posted!