Kits are readily available.
Type these 2 words into Google:-
Transformer kit
(1) RS components in the UK sell transformer kits
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They show a 100 VA E + I kit for =A331.95 UK
(2) Maplin (UK) sell an E + I kit for =A316.66 UK price, delivery extra, no mention of frequency.
[quote] A transformer kit having a ready wound 120-240V mains primary winding, E and I laminations, end frames and clamping bolts. Secondary windings can be wound using enamelled copper wire for a total power output not exceeding 100VA. To find the number of secondary turns required, multiply output voltage required by 4.16 turns per volt, +1% for each multiple of 10VA loading. Wire for winding the secondaries is not supplied in the kit. Dimensions: Width 89mm x Depth 68mm x Height 75mm. Weight: 1400g. [/quote]
(3) A US firm called Toroid Corporation of Maryland sell kits 80VA =3D $30,
1400VA $106. "Made for 60 Hz" it says.
[quote] The many advantages of custom designed toroidal transformers are now available to you in small quantities with little investment required.
When our standard transformers are not suitable or when exact output data cannot easily be established, you now have a less expensive alternative to a full custom design. Toroid Corporation offers kits with factory made primaries, available in five power ratings and come with complete instructions. All kits are made for 60 Hz operation.
(1) Calculate Volts x Amps (RMS) for each winding. The SUM of these VA-ratings must be smaller than the rated VA for the kit to be chosen. (2) Rated DC power replaces the VA rating if the transformer is used to supply rectifiers with capacitor filters as loads. Calculate PDC =3D (DCVolts + 2) x DCAmps for each bridge rectifier supplied by the transformer. The SUM of the PDCs for all rectifiers must be smaller than the Rated DC Power for the transformer. If any rectifier uses two diodes and a center tapped secondary instead of a regular bridge conversion, its PDC is: 1.4 x (DCVolt + 1) x DCAmps.
The kit does not include magnet wire for the secondary windings. (Available from motor repair shops)
Options The price for the kit (please see chart) does not include engineering assistance to calculate wire size and length. Should you like us to do this work for you, we would be happy to help you for a fixed fee of $175.00 per design. Required magnet wire would then be shipped with the transformer kit from the factory at no extra charge. [/quote]