Mudd,
for reference you can usually dismantle a counterbalance valve and use pieces of it to to block the cavity.
On the assumption you have a sun counterbalance you can dismantle it in the following manner. NOTE: Do NOT damage the hex portion of this assembly or the O-rings on the hex portion you will need these.
1) turn the adjustment to remove all of the spring pressure. For Sun this is typically clockwise. Tighten the jam nut on the adjustment.
2) look at the bottom of the threaded portion of the valve which i will call the retainer. There should be a slot that is partially crimped shut approx 1/8 - 3/32 from the end of the retainer. Pry this slot open.
3) hold one end in a vice or a Collett with the slot where you can see it easily. this makes the next step easier.
4) Now slowly turn the part not in the vice while looking at the slot. You should see a wire ring in this slot, one end is bent at 90 degrees and locks into the round portion of the valve that I will call the cage. keep turning the part until you see the cut end of the wire ring. Use a dental pick to pry up the end of the wire ring and then turn the part to unwind the ring out through the slot.
5) remove the wire ring and pull the two pieces apart. This might require a slight twisting and rocking action. A spring will be loose in the retainer so remove this also.
6) Valve dismantling is complete.
Now comes the harder part. There is a small drilled hole in the retainer From memory it goes in at an angle close to one of the O-ring grooves. This is the pilot hole that connects the rod end port and pilots the C'balance valve open. You must some how block this connection. You might be able to tap the hole in the cylinder that connects to the valve cavity or else you will have to plug the hole in the retainer. This will see the pressure on the blind end of the cylinder.
Once this connection is blocked, screw the retainer back into the cavity and you have successfully removed the C'Balance valve and can use the existing ports on the cylinder.