Look at the Winbond part W78E516BP-24. It is available now thru All American Semiconductors at www.allamerican.com
The winbond page describing the 8-bit micros is:
www.winbond.com/product/index.html
I think this is the foundry that fabricates chips for Dallas Semi because they now offer the "Turbo-51" series of controllers that are the exact copy of the old Dallas Semi parts with dual DPTR, 1K ext ram on chip, and 4 clock cycles per instruction though the turbo parts have an 8 week lead time.
I know that the W78E516BP-24 are in stock because I just ordered 12qty today.
Sincerely,
Buck Stein