WHERE CAN I BUY KNITTING MACHINE PARTS?  

Linda Williams of Country Knitting of Maine is a Silver Reed and Brother dealer.  Contact information is on her website Countryknittingofmaine.com 
Needletek. Their email is Ndlteknew@gmail.com
One or our favorite machine knitting teachers also runs www.dknits.com The parts available are not all cateloged on the website. e-mail Michael Becker with your needs. He is responsive and knowledgable.
Peter Patchis sells Taitexma knitting machines which are copies of old Brother models. Many of the parts will work to keep your old Brother going. E-mail or call him to express your needs. www.peterpatchisyarns.com
Leeanneco on ebay sells lots of Brother parts and some othe knitting machine parts. Very fast delivery.
Sunny Choi is an etsy seller based in China. He manages to ship fast to the US and Canada in spite of the distance and we have had good experiences. His etsy name is HongKong Knitbox. 

WHAT ABOUT REBUILDING SPONGE BARS? It works great IF you use the right stuff. Unfortunately, I  no longer have a reliable source for the sponge that really works well.