Fetching PKs is a very common solution to the problem that you've mentioned. A very popular solution is to have a table that contains the next key value and a stored procedure to fetch/update it.

CREATE TABLE ID (token varchar(40), nextid integer)
GO
CREATE PROCEDURE GetNextId
 @table varchar(40), @id integer OUTPUT
AS
 UPDATE id
 SET @id = nextid, nextid = nextid + 1
 WHERE token = @table
 
 RETURN 0
GO

-Mike