Another good source of stainless steel rod, cold rolled steel rod and 80/20 rail and fittings is Zoro (zoro.com). Prices have definitely gone up in the recent past, and are now about the same as McMaster or a little higher.
Zoro’s biggest advantage over McMaster is they have ubiquitous 20%-off coupons, free shipping over $50.00 and $5.00 shipping on anything under that. Their website is not nearly as organized as McMaster’s though.
Shipping can be kinda weird. I placed an order of mixed steel, machinable steel, and stainless steel rods in different sizes and three days later UPS showed up with maybe six different cardboard tubes of materials. I presume they all originated in different warehouses. No way would $5.00 have covered that shipping.
My 8 foot piece of 1” clear anodized 80/20 rail cost me about $10.00 ten or twelve years ago. Alas, no more.