There is just one word in the OED that begins Compra-, even though it sounds a very plausible cluster of letters, and there is no problem in pronouncing it. The word is comprador, which has its origins in the Portuguese word for 'to buy'. It is, as the OED says, 'one of the Portuguese words adopted in the East' and is defined as both "Formerly, the name of a native servant employed by Europeans, in India and the East, to purchase necessaries and keep the household accounts" and "in China, the name of the principal native servant, employed in European establishments, and especially in houses of business, both as head of the staff of native employés, and as intermediary between the house and its native customers".
The reason I discovered that word was because I was looking up comprachico, which I came across earlier (and which is not in the OED). This word was coined by Victor Hugo in one of his lesser-known novels, The Man Who Laughs. It is based on Spanish and means 'child-buyers'. The comprachicos were supposedly people who deliberately mutilated children and then had them earn money in fairgrounds. This is from the book:
The Comprachicos traded in children. They bought and sold them. They did not steal them. The kidnapping of children is another branch of industry. And what did they make of these children?
To laugh at.
The populace must needs laugh, and kings too.
In The Man Who Laughs the mutilated boy has had a permanent grin cut into his face.
Ayn Rand wrote an article entitled The Comprachicos. She uses the word to describe educators, believing that children are actually stunted and degraded by the pedagogical methods used in schools (read more on page 325 of this book). That was the sense I came across earlier, when I was reading an article and its comments about school teaching methods (and which I now can't find, I'm sorry).