Wise decision, to lap any new barrel.
  The lap compound is listed as 'lap kit' .  Price is $18.50 plus shipping.  You'll need lap bullets too, and any 30 caliber mold will make good ones.  If you don't have a mold, contact me at LBTisAccuracy@Imbris.net and I'll quote you a price for lap bullets, shipping etc.   We used to sell them, but took them out of the catalog, but we still have probably a ton of them, and can supply for most calibers.