(Looks at Sentimental Journey site, sees prices, faints.)
The original "Aerial Rods 'F'" were push-fit and tended to come apart when travelling across country. The Canadians (I think) improved them by adding an extra 1.5 inches to the length and incorporated a rolled-in thread at each end.
Those were in general use later on in WW2, remained in service during the Larkspur era, and were still in production in 1981 - possibly later still - they are in the RACAL Antennas catalogue of that date.
Clansman saw the introduction of a metric version, the rods being 1 metre instead of 48 (or 49.5) inches long but the specification is the same and they will all fit (as far as I'm aware).
It's probably easier (and a lot cheaper) to get them in the US or (especially) Canada, as there will still be Lend-Lease surplus tucked away in odd corners, plus Canada used Larkspur initially.
This is my table of "what's what":
Aerial Rods 'F'
ZA.0894 No.1 (Bottom)
ZA.0895 No.2 (Centre)
ZA.0896 No.3 (Top)
ZA.44684 No.1 Mk.1/1
ZA.44683 No.2 Mk.1/1
ZA.44682 No.3 Mk.1/1
Z42 5820 99 949 1166 No.1 Antenna Rods, F. Mk.2 - bottom = ZA.44684
Z42 5985 99 949 0985 No.2 Antenna Rods, F. Mk.2 - middle = ZA.44683
Z42 5985 99 949 0995 No.3 Antenna Rods, F. Mk.2 - top = ZA.44682
Racal Antenna Catalogue 1986
Section Steel 1 metre Steel 1.2 metre Fibreglass 1 metre
No.1 (bottom) 5985-99-630-8455 (MA681) 5985-99-949-1166 5985-99-649-8138 (RA746)
No.2 (middle) 5985-99-630-8456 (MA682) 5985-99-949-0985 5985-99-649-8139 (RA747)
No.3 (top) 5985-99-630-8457 (MA683) 5985-99-949-0995 5985-99-649-8140 (RA748)
Carry Case 5985-99-745-3190 5985-99-102-3666 5985-99-745-3190
(Okay, so it was a table before the MLU "space eater" snacked on the formatting.)
Best regards,
Chris.