I usually make my custom molds from soft two component silicone paste with a tan color. I press it together and knead it. Put it in my ears and 30 minutes later: voilá, soft ear molds!
Neat idea you are doing for molds.
I got a few hits using translucent in the search.
I only got liquid silicon, no kneadable paste. Could you pm me a link?
Search… Pebeo - Gedeo Siligum Silicone Molding Paste - 100g
Not sure about color but you could ask.
The translucent came liquid for me too.
That one is blue and is a bit overpriced on Amazon. It’s the same as the one I ordered only 3/2 of the price and 2/3 of the weight.
I am sure the pigments are added to make the mixing more obvious, but I really would like translucent/transparent silicone gum!
I use a 1mm drill for the vent. A 1.5mm for the hole of the thinwire and a 2mm for the start of the hole of the thinwire so that it can be pushed further inside.
The old paste was reddish, the new one blue, I would like to have transparent, too, though.
Zebras would love your molds.
Have you considered finding someone to make molds for you?
Yes, the labs seem to ask about 25€ for it. You can get impressions from the aid dispensers for about the same price. However, when you ask them to get the molds for you it is about 140€: My audiologist was shocked. He asked me whether I wanted a document which stated what materials the labs would accept for their molds.
(He also stated rather firmly that if the lower frequencies in the AudiogramDirect went up in dB, the molds weren’t fitting very well. And that if all the frequencies went up, I better get back to him.)
Anyways, still haven’t found a local lab that will make soft transparent molds.
I get my soft silicone molds from a business here in the USA. They mail the materials and instructions to make the impressions. I make and mail the impressions back to them. They send them out to be made with 3D equipment. When they get them back they are mailed back to me.
This process takes about 2 weeks. They are guaranteed to be right. I did have to have one of mine remade that turned out great.
These cost me about $110 US.
Zebras has mentioned she gets hers made near her. England isn’t too far from you.
Zebras also mentioned that the person who makes them for her, is a friend of hers. 
Still seems rather roundabout. Why can’t you just use the impression material? just drill two holes in it. You can even experiment with what you prefer for a vent size.
I have thought about molds for a long time.
When my hearing got so bad that I had to have molds it was time to do something. I had not read anything about making my own but learned about Lloyd’s here in the states doing it. So that’s the route I went. Lloyd’s has been absolutely wonderful. Great bunch of people.
@Markismus Have you thought about using www.arlingtonlabs.co.uk
I send my old ear moulds for them to make moulds.
Try DETAX Audio? They sell all sort of materials for hearing molds and its production
