Deborah,
You said: "He was born in Sampelburg, Germany..."

I suspect that the town you are looking for is Zempelburg, now known as Sepólno Krajenskie in northern Poland.

familysearch.org has some films of civil records, but they cover a later period, and are only viewable from their libraries. They don't seem to have specifically Jewish records from the town.

My advice would be to look for American records - the marriage and death certificates of Morris and his siblings. They should name his parents.
Jewishgen's databases include the West Prussia citizenship list of 1812. This is one or two generations earlier than you want, but it includes 19 Lehmanns, one of whom lived in Zempelburg. Leyser Lehmann could be the father, grandfather or even great-grandfather of Moritz, but any of the 19 would be candidate ancestors.

I hope this helps,
Rodney Eisfelder
Melbourne, Australia