Hi, AL
I got replacement valves from an internet vendor. Type iPlumb.tv and when that comes up type Pex fittings Flair-it Bulk. When that page comes up scroll down to the bottom of the page. The valves I ordered are at the bottom of the right hand column listed as MNFLD VLV 1/2FSWV X 1/2M X 1/2 Stock #06917, Price $11.35 EA
You can but any individual part for those valves. Mine came with white plastic handles but your existing handles fit. Very nice people to deal with and excellent service. I got the lead for this vendor from this forum. I wish I could remember who to thank, so whoever you are, THANK YOU.
Hope this helps, Sam