How can i fix my lift up bed?

I bought a gas lift storage bed kingsize about 4 years ago. The trouble is the bed is getting harder to lift up. Parts need replacing. I have spent hours online trying to get/buy the parts (gas pistons??)don't know if that is what the parts are called!!The bed shop where i bought the bed from has now gone. So you can see i have not got a clue.Please, where can i buy these parts. Do you know where i can get them from online? Assuming they are called gas pistons, gas lifts etc. Please could you help. Any advice would be greatly received as i am very scared this bed will fall on me!!!!
This action (Gas lift) is what keeps the bed/mattress upright, so the storage underneath is easily accessable.
Look forward to your reply,
Many thanks,
p.s you are my last hope!!!