INDEX/MATCH with multiple criteria -- if value isn't found, ignore it, and search for something else

I *think* this is what you're looking for:

=INDEX(Price, MATCH( IF( ISERROR( FIND("/",Division) ), Division, TRIM( LEFT( L11, FIND( "/", Division)-1 ) ) ), Size, 0) )

For INDEX-MATCH, the logic is: Index on the price by matching a calculated value in the Size column, using a match-type of zero. 

For the calculated value, the logic is: If "/" does NOT exist in the Division text, return the Division text. Otherwise, return the TRIMmed text before the "/" in the Division cell. 

=INDEX( Price,
               MATCH(
                   IF(
                        ISERROR( FIND("/", Division) ),
                        Division,
                        TRIM(
                            LEFT(
                                     L11,
                                     FIND( "/", Division)-1 ) )  ),
                Size,

                0) )