A few months ago I saw an Aliexpress seller that had lots of different colour baseplates, which are the lego pieces typically used for modular building. Anyways, they had quite an assortment and the price was reasonable, so I placed an order for a couple just to see if they were any good or not.
In the past, baseplates that I have ordered were flimsy and came without any packaging. These new ones were different. Each baseplate comes in it's own packaging and the quality is excellent, exact Lego quality. The brand is called LOJO and the item number is AX1001. Anyways, I swapped out the crappy baseplate that came with my Lepin Cafe Corner and used the LOJO one. Wow, what a difference. They are very sturdy and don't bend much despite not being that thick. Here's my latest order.
The size is 32 studs by 32 studs and will support your fullsize modulars.
As you can see, the baseplates are on sale for only $3.39 USD and come with free shipping.
Where to Get it
If you are interested in getting some decent and cheap baseplates for your modular town, get these LOJO brand ones from here.
Please remember that I cannot verify whether the seller or the item featured is good or not. Use your own judgement and research before making any purchases. I have no affiliation to Aliexpress or the sellers found there.