So, last thing is first. If you cannot do the woodworking yourself, you are stuck looking for what is known as a flat-pack or you want to have a smaller vendor drop ship to you (not necessarily cheaper, these are heavy and shipping can be expensive depending on the design).
As such, you are either going to have to glue it yourself, or you have to just buy a different pair of speakers. If you want a recommendation on affordable bookshelves, go back through Toid’s videos or check out Erin’s picks. https://www.youtube.com/watch?v=j3ZWkJdTwdk
That is his favorites under $400 and he has Klippel data on each model along with reviews. You cannot beat his data, although there is more to data to consider, such as whether you like a “V” profile (drop in the mid-range) or how it might interact with your room. But, generally, the more neutral the more better.
You may be able to talk Toid into making you a flat pack to assemble yourself (due to size, flat packs often will cost less to ship than assembled speakers).