If you do print up mats of some kind in reverse and want to make rubber ones , then corn starch is the word of the day.
2 pack silicone rubber is expensive.
But a cheap option is to buy roofing silicone , mix it with turps and corn starch , and voila ! You have your own rubber.
Spray mould release to your master , make dams around it and pour your rubber on to the mould .
I have tried it , yes it works , but google it or search YouTube to get the right mix ratios to obtain the rubber hardness you desire.
Corn starch from the supermarket does just fine.
Ps check out
www.barnes.com.au for accessories