I am attaching the latest 7.2.1 code for each platform for sppr_sys_reservequeueitem_b here. It's safe to replace the out of the box version of this stored procedure in any 6.x or 7.x release up to 7.2.1 with what I have attached.
To make the performance improvement, you also need the following 7.1.x OOTB indexes. These indexes are different depending on which database platform is in use.
Note: you need to properly schema qualify these statements with your prpc data schema name for both the indexes and stored procedures.