The Primus mortise cylinder is probably by far the most readily available Primus lock online for decent prices. My favorite place to find these is doing an Ebay search for "Schlage primus". Usually you can find them for roughly $25-$30 a piece without keys($40+ With keys). Read the descriptions and make sure they have pins in them and are not just "sub assembled".I also pay attention to the keyway it may be an Everest primus despite the ad stating "Primus".

Progressive Pinning

This is by far the most recommended method for learning to pick Primus locks. To get accustomed to moving a pick around a Primus, you'll want to empty all of the pin chambers. If your lock came with working keys, make sure to keep each chamber separate. If you mix the pins up, your key will not work again until the pins are back in the correct chambers, orientation, and order. If your lock did not come with keys, you can mix them up all you want.

Now, pick any finger pin and any spring. What we're going to do is put one of the finger pins back into chamber one, Flip the core upside down drop in the spring in to the smaller chamber closest to the front of the keyway and then drop the finger pin after it, there is a small hole in the top of the finger pin for the spring to rest in (With ear facing in to the keyway and the larger end touching the core wall) then re-assemble the sidebar and springs in to the plug (sidebar has no right way, Sidebar springs will be significantly smaller than the finger pin springs or top stack springs) then reassemble the rest of the lock, You've just pinned up your first practice Primus lock.

Use your tension tool to tension the lock, and use your pick to slide under the finger pin. Under moderate to heavy tension push or pull the finger pin away or towards you (to pull hook the finger pin ear with the finger pin pick) then position the pick as center to the finger pin as possible and lift the pin slightly, then do the opposite to the push / pull you did before to "sweep" the finger pin from full left to full right or vice / versa. Continue to do this motion until you get an open. If you feel you have over lifted the finger pin slowly release tension until you hear a click of the finger pin dropping and start over until open.

Open the 1-pin Primus a few times until you get the hang of what's going on in the lock. Now put a second finger pin, and spring in chamber #2; repeat the previous step until you get the hang of a 2-pin Primus.

Once you feel pretty good about 2-pin Primus, put a third pin set in the lock, but instead of using chamber #3, put the third set of pins in the farthest chamber in the lock. This will let you practice reaching into the back of the lock and manipulating a finger pin that's not so close to you.

Now that you're opening a 3-pin Primus pretty regularly, you're pretty much set.. If you can open a 3-pin Primus, you can open a 5-pin Primus. More pins do not add to the difficulty, only to the time required to open the lock.

Before you jump to a 5-pin lock however, you need to practice with the top stack. Remove all the pins from all the chambers. Put any keypin in the first chamber, and then a standard driver on top of it, and fill chamber #1 for the finger pin. Use your tools to lift the keypin until it sets, you should feel slight rotation on the plug. Then move to the finger pin and lift / rotate like before.

Continue picking and pinning the Primus until all chambers are filled.