I know this post is a year old but it is the only thing that came up when I googled the same problem.
I found the original suction cups.
Get them at
William B. Rudow, Inc
Suckers.com
Part number: 1514-1709-4
Brand: Muller Martini
Get them from Graphtec UK for £27.58 for 2 and who knows how much shipping because they don't ship to the US so you have to find an expensive work around, or get them from suckers.com for $1.50 each. The only downside is their website does not have a cart so you have to email or call your order.
I ordered 20 for $30
https://www.suckers.com/suction-cups/round/1514-1709-4/?back=suctionCups