Better late than never trying using a product from Resins online called EL420CR/NC. It is a very runny ultraclear 2 part polymer which sets to a semi rigid UV resistant mass that mimics water. It is easy to mix and process.
It will hold all types of artificial flower stem and sticks well to glass and ceramic.
Either google Resins online or call the supplier Robnor Resins their tech support is very good.