Vinyl window balance #2630

I've purchased replacement tension rods however they came without the plastic pieces at either end. The recommended pieces that I ordered from another company don't work with my window. I apparently need the exact pieces shown in these photos for two tension rods.
Also, the previous kit came with rivets to hold the plastic pieces on but I don't have a way to splay the one end of the rivet once it's through the tension rod to secure the plastic piece. Any suggestions?
Thank you.