Honestly I would try and replace it with vacuum hose.
There are places online that sells plastic vacuum tubing but I dont know what size that would be. I personally am getting rid of all the plastic vacuum tubing on my truck and just going with proper sized vacuum hose. Mine isnt bad nor brittle on my truck but its only a matter of time.
"Old Blue" - '56 Fairlane Town Sedan - 292-4V, Ford-O-Matic transmission, 3.22:1
'63 Belair 2dr sdn - 283-4V, Powerglide transmission, 4.56:1
'78 Cougar XR7 - 351-2V, FMX transmission, 2.75:1 9inch
"Bruno" - '82 F150 Flareside - 302-2V, C6 transmission, 2.75:1 9inch, 31x10.50-15 BFG KO2