。
I'm looking for a leather shoulder bag.
Literal
Leather shoulder-bag [object-を] looking-for [explanatory-のですが].
革のショルダーバッグ mixes Japanese 革 ('leather') with the English loanword ショルダーバッグ ('shoulder bag'). ~のですが uses explanatory の with が to soften the statement into a polite, indirect request — a common shopping pattern.