SkiffRopes sell the new Allen 30 Extra High Load Boom Vang Block for $230.
See manufacturer product info at: https://www.allenbrothers.co.uk/product/30mm-extreme-high-load-block-with-a-873/
See product drawing at: https://www.deckhardware.com.au/assets/brochures/A2031XHL-873.pdf