Foster, who plays out of the same Worksop Golf Club as Westwood, carded a 68 on the final day to secure him a one-shot victory at 14-under-par 278.
'I played three rounds of golf with Lee before coming to Zambia, so maybe that helped me,' said Foster, who has played on the European Challenge Tour for the past five years.
Jaco Olver shared second place with Englishman Stuart Little on 13-under 279. Olver produced the round of the tournament when he picked up nine shots on his overnight score and came surging through the field with a 64 on the final day.
The young Johannesburg golfer seemed to have done enough for victory when he carded five successive birdies from the turn. But waiting in the clubhouse, Olver knew that a missed two-foot putt for birdie at the 18th might cost him the tournament, with Foster securing the victory with a birdie on the 15th.
'I was in the running all week, and kept myself just behind the leaders going into the final day,' the 25-year-old Foster said. 'I wasn't fully aware of what Olver had done ahead of me. My main concern was Stuart Little. He was playing really well on the back nine.'
Foster started the final day two shots off the 11-under-par lead of Little. But after three holes, Little had dropped a shot and Foster birdied the par-5 2nd, with Graeme van der Nest joining them for a three-way tie for the on-course lead at 10-under-par.
Foster went on to birdie both the 4th and 6th holes before dropping his first shot of the day at the 8th, where his drive finished in the trees forcing him to chip out onto the fairway.
But three birdies on the back nine was enough to clinch him the tournament.
Foster added : 'I've never putted on greens as grainy as these - they were a really tough part of this tournament.'
Olver's joint second place finish is his best in two years as a professional, improving on his fifth place in last year's Royal Swazi Sun Open.
'This is easily the most memorable round of my professional career,' Olver said of a round, that included two chip-ins for birdie on the front nine.
The Sunshine Tour remains in Zambia for this week's Cock of the North tournament at the Ndola Golf Club.