Outdoor Decor - Help me find this!

The first one was a bespoke design from Jem & I:

http://jemandi.com.au/custom-designs

The second was one from Sweet Brothers Events:

https://sweetbrothers.events/product/acrylic-welcome-sign-foliage/

I suspect the boxes were built by the companies that made them, rather than being a stock item you could find in a store.

Cannot vouch for the retailer, but maybe you can work with this: https://www.shoppopdisplays.com/P_PED-ACRYLIC-CLEAR-FLAT/clear-acrylic-pedestal.html?v=35321&st-t=adwords&vt-k=&vt-pti=324343382863&gclid=CjwKCAiA3uDwBRBFEiwA1VsajPLCfSDqTf7TMK39oiZIYVdhXG8BxpFSVwObqrYsXG8Hsp9gniX8_xoCQUoQAvD_BwE


Search for large acrylic container and you’ll get some ideas. Or try asking a florist, since your examples are floral.

Most craft supply houses only have small terrariums or display cases, like https://www.save-on-crafts.com/terrarium-containers.html
But large floral supply houses have kits with edge brackets, acrylic glue. Or Glass, though those are hugely expensive .
If you know someone who has a workshop, and tools, most home warehouses that have lumber also have sheets of Lexan or another clear plexiglass. My dad buys sheets, used saw and drill to cut sections, brackets and hinges, and makes 30-48 inch long bird feeders to hang outside windows, see through.

If you to build things, or have someone who would do it as a wedding gift, Dad says: Lexan clearest, more like glass, next is Optix acrylic. Some of the cheaper ones look dimestore cheap, so inspect them before they are purchased, to be sure before going by lowest price. And a reminder, if there is the slightest bit of sun, like glass it heats up. Pro floral ones that may be in sun have refrigeration u it's under, for real flowers. Silk take more temp variation by a lot. I had forgotten that some of the cases for his carvings, and a large hinged tabletop box 24x48 a relative uses for jewelry taken to craft shows, he built when I was young. I remember him making the feeders. But the hinged display boxes, taken care of, are still clear, nice, after many years, made of Lexan. And though the proper adhesive is used on corner edges, each edge joining has a bright gold or silver bracket, or hinges for the open part. .......These Lowe's prices are fairly standard for big box lumber. Local lumber supply places may charge you more, but cut sheets for free, a few cuts. Or charge the same plus a couple dollars per cut.
So , table height being 28" about:. a tower 48" high, and 24" wide sides, and 24"x24" at ends top and bottom, would take one 48"x96" sheet plus one 24"x48".
And for a 36" high tower, with 18" side width and 18"x18", would take one 36"x72" sheet plus one 18"x36" sheet. .....Not all that expensive. Plus lettering paint on with metallic paint, or a sign. And brackets and hinges. And 4 saw cuts per box, if they do them. And box builder does the rest, adhesive or drilled. Or buy materials, but hire someone.