There seems to be a lot of rhyming slang for all types of money, the rhyming slang is often rhyming another slang word.
So a pound is often referred to as a quid, a term dating back to at least the 17th century. It is thought that it derives from the Latin word quid and possibly from the phrase "quid pro quo" but no one has established a definitive derivative.
So "teapot lid", "saucepan lid" (phrases also used for "kid") are rhyming slang for quid, as is 'squid'.
A 'nicker' is also slang for a pound, originating in horse racing and gambling circles, I have a feeling that this may derive from nickel as small pieces of metal were thrown down to signify a bet being placed.
So for nicker, rhyming slang has "cherry picker" and a few other obscure ones.
For pound itself the most common is "lost and found" or "hole in the ground".
In summing up, rhyming slang for a pound is not as common as general slang for a pound. I have also heard terms "funt" (based on the German or Yiddish) and even more confusingly "dollar" which can also be used as a more general term for money and often only used in the singular.