The small bearing on one of my Novas' saftey was missing when I got it. They are hard to find if you were to go looking to purchase one. You best bet would be to try a gunsmith that works on real guns, many real guns use these same size bearings.
Or I could tell you where I finally found one...it was already in my gear bag and you probally have one in your gear bag or tool kit. If you have one of the metal protector caps for a HPA fill nipple, or a quick disconnect from a remote air hose you most likely already have the size that you need. Just take the snap ring off the connector and you will have at least one and with some connectors you will have as many as six bearings.
As for the spring, just get one that will fit into the hole and you will be OK.
If you can't get it to work, get with Avery, he bought all my Nova stuff from me last year. He has probally the biggest collection of working, non-working, and parts for the Novas than any one else around.
Hope this helps