I also wanted to add that I used a canner to provide steam until I purchased my Jiffy steamer from Amazon for under $50. I can't remember the exact price off the top of my head, but it was very affordable. You can also use a variety of items like spoons etc. anything that you can heat and a hot plate to mold flower petals.
I think a simple dome and brim block would be best, when looking at blocks, I have a cloche set that I use more than anything.