I know that giving bombers or cruise missiles to NKorea will provoke pro-US country around China like SKorea and Japan and US itself, but I think China surely needs good arming ally in this region, regarding Taiwan issue if pro-US country around China join forces with US against China. It happen in Korean war remember? if there is war in this region, caused by NKorean provocation or Taiwan issue or South China conflict or Eastern China conflict with Japan, China will troubled without nearby kick-ass sidekick.
Just my opinion... it is pretty stupid to give away equipments, no matter how insignificant those items are to any third party countries unless they could afford to buy it from you at full cost.
One option that I believe China would be taking was to request their troops to be stationed in NK. If NK need those equipments to protect themselves, then with very well armed and equipped Chinese troops in their country, it would give them the necessary security and China could use this small country as a leverage to other pro-US nations.