Hi,
I've made some mesh triangles out of curtain netting using the damaged ones as templates. Try and get some quilters tape this is double sided tape which dissolves during washing. Trying to pin velcro onto netting is fiddly and the pins tend to fall out, using the tape ensures that the pins have something more substantial to grip onto.
Having cut your netting to the correct size, edge the whole thing with the tape, peel off the top protective strip and stick the velcro onto the tape, then pin as the adhesion is not great. Sew together, launder so that the tape dissolves and hey presto new mesh triangles.
Good Luck
Denise
P.S. I recycled the velcro from the existing mesh and got the net from a charity shop for 50p the quilters tape I already had total cost £1.00 max