30 x 30 Sump Basin - Where Can I find One ?

Currently have a single 18x22 Basin and need to change it
( Need to have a secondary pump for protection and want to increase cycle time )

The contractor is worried about going too deep as I have a very high water table
I've seen 30 x 36 but wanted a 30 x 30

Does such a beast exist ? Where can I purchase one ?

Thanks

I don't know but a 30 x 36 minus 6" makes one.