I have panniers similar to Alpos. They came without any fittings attached, but the supplier supplied his own attachment kit which would have been fairly easy to make. Difficult to describe without photos but here goes:-
My pannier frame is similar to Touratech/Metal Mule etc in that it is made from 18mm tubing and forms a rectangle held in place either side of the rear wheel.
I have 4 round plastic blocks for each pannier 18mm deep and about 50mm diameter.
2 fixed pieces of aluminium bar about 50mm * 70mm per side
2 pieces of aluminium about 70mm * 25mm per side.
The 4 plastic blocks are screwed to the inside of each pannier so as to located it within the frame. I reinforced the inside face of each pannier with aluminum strips between the mounting points
The wider aluminium bars are fixed with the bottom blocks to form a lip to hold the bottom of the pannier in place.
The narrower bars are pivoted on a longer bolt through the centre of the top blocks. The bolt is fastened on the inside by a large knurled nut which can be unscrewed by hand from inside the pannier.
To fit the pannier, the top plates are loose and dangling down so the pannier can be placed against the rack with the plastic spacers in position. The top plates are then rotated to point upwards and then the knurled nut tightened from the inside. The top plate can't move anywhere as the nuts and bolts which hold the plastic spacers in place prevent it from swinging once the knurled nut is tightened.
The only part which would be hard to make without a lathe would be the knurled nut and an ordinary nut would do the job, just wouldn't be as convenient.
My only criticism is that the knurled nut sticks out into the pannier and gets in the way.
The best method I've seen is on Metal Mule. It's a kind of lever system which locks a bar against the frame and is held in place by the lid.
If you think you are too small to make a difference you have never spent the night with a mosquito.