I once built a "grease bank" for a DMI field cultivator. I tried the plastic air lines that someone suggested here in another reply. The grease will soften the plastic & then it will "blister" & pop eventually. I thought it was a good solution at first, until the lines softened in a couple of days.

The "soft copper" tubing turned out to be the best & most economical solution. You can cut it, route it, & use compression fittings & get the job done. The copper held the pressure for me. My experience showed me that the zerk would give up & leak past the jaws first if grease flow was hindered. Probably the only downside I saw to the copper might be accidental crimping of the line. You might not realize it & prevent grease flow & blame the wrong target.

Soft copper is what you buy @ plumbing supply in rolls & has corresponding compression fittings. Hard copper could be used for long straight runs, but you have to solder the hard copper normally.

Good luck.