I think Global Sugar Art carries the pans, and so does Beryl’s - I’m sure it is just a matter of time before other distributors carry this pan. In Australia, I would check in with Iced Affair. I’ve bought from them in the past and they are very helpful, extremely nice and I couldn’t believe how fast the cutters arrived!
What I do is bake off sheet cakes - usually half sheets. I bake in 2” high pans. I torte the cake into two layers, sometimes three if I use the 2.5” high pans I have (I had them custom made, I’ve only got 6 of them). Once they’re torted, I use my round cookie cutters to cut the circles, or a long, very firm/rigid ruler if I need squares. Rounds aren’t too bad, squares are horrible. All those edges/corners….
I use one layer of filling for the bottom and middle cakes. The top tier is just a thimble of cake, it’s not layered with buttercream. That would drive me over the edge. It is much easier to do this in stages. When I have orders for mini cakes (the last one was last summer, 300 individual three tier coconut cakes. Thankfully they were coated with coconut! It took me the entire week to do.) Bake a day earlier than usual; make buttercream the next day (you always need twice as much as you think you do), and start assembly on day 3. Depending on how many you have, you might not get to coating them with buttercream on day 3, so wrap in plastic and store overnight. Then Day 4 is coating w/buttercream, Day 5 is covering with fondant. Suprizingly, putting fondant on goes very quickly with small cakes - at least for me it does. When I make mini cakes, I use a 2.75” bottom, 2” middle and 1” top. But I usually like to keep them to two tiers; otherwise they are harder to handle and to eat. So for two tiers, do the top and let them chill. Then when you coat the bottom tiers, you can put the middles on when the buttercream is still soft and you don’t have to use something to keep them together.