Well, it's that time again, Miranda is 17 months now & our nursing relationship is waning. Soooo, to put it mildly, my giganto nursing bras are overkill for my current endowments. I have 2 drawers of bras in sizes from AAA-DD, & most I've not worn in nearly 3 years. I know, it's clutter & I hate to ask for money for smaller bras when I've so many but none of them are for nursing & I do plan on nursing until she's 2. So, you can find these elsewhere, I found one in Cyrillic & the pictures were easy enough to follow, but here it is in English.
Fist select the right size bra to convert. I thought I'd practice on a cheapy one befor trying this on a prettier one. Slice off one strap.
Remove the nursing clasp from your rattiest most worn-out nursing bra that does nothing for proper support and/or the wire that mercilessly pokes you no matter how many times you sew it back in. Loop it through a piece of satin ribbon & sew to the top of the cup. You can certainly machine sew this, but I'm hand sewing in order to not scratch poison ivy/ prednisone during a movie.
Measure (keeping some extra) & sew the ribbon satin side out down below on the elastic taking care to align it w/ your clasp above.
Do make sure you've gone over & bound or zig-zagged the raw edge you created by cutting the strap.
Hmmm, I didn't take the picture showing the clasp being secured to the strap. Do that, secure it to the first clasp you sewed to the bra cup then pull the ribbon through & sew it together.