Hi
Clwyd FHS once produced a CD of Nonconformist records in the area. I have the one covering the old Denbighshire (The Blackwell index). I don't think it's available for sale now. I copied it to my PC. However, the only records that are available for Llansilin are of the Bethesda Congregational Chapel. This covers Births/Baptisms from 181-1837.
I've not used it for a while but can have a look for you.
However, if the records that you are looking for aren't available in the online Non-C records, it's unlikely that they have survived.
It might be worth contacting the Clwyd FHS -
https://www.clwydfhs.org.uk/Gadget
PS - note that many nonconformists went to other areas for baptisms, etc. so they might be under Llangollen, Oswestry, etc. I found some of mine in Llangollen listings.