The likes of Amidon:
http://www.amidoncorp.com/43-materia...perture-cores/
still offer their range of 'classic' binocular ferrites.
You don't strictly need a two-hole ferrite for winding the balance-transformers: two single-hole beads side-by-side work rather well.: I've built bifilar transformers for the crystal-filter in SSB generators using this technique and found no difference compared to a binocular.
In the past I also worked on a range of HF/VHF power-amplifiers whose 'balanced' push-pull driver/output transformers were made from two parallel lengths of silver-plated copper tube about 3/4 inch diameter, with sets of ferrite rings threaded over them, and silver-plated copper plates silver-soldered to the ends to provide a 'single turn' - PTFE-insulated coax was then threaded through the holes to provide the primary winding.