Alvis took the lead in the 15th minute when a corner from the left by Joss Holford was met at the far post by Sean Martin, whose header went in off the woodwork, despite the efforts of Ryan Isherwood on the line to keep the ball out.
It took until the 27th minute for Saints to have their first shot on goal. A cross by Josh Turton was flicked on by Kurt Parsons to Oli Manoochehri, but the striker put his shot over the bar.
Saints levelled three minutes before the interval when a free-kick by Danny Wylde was headed on by Steve Thomas and Parsons rifled a shot past Chris Woodward into the corner of the net.
With the clock ticking down, Woodward made a good save to deny Manoochehri, before substitute Donaldson hit a shot low from the left which went in off the near post.
On Saturday, Saints tore up the formbook when twice coming from behind to win 3-2 at fourth-placed Bolehall Swifts.
It did not look too hopeful for Ian Ray’s team when they fell behind in just the fourth minute. A simple through ball opened up a big gap in their defence and, although keeper Tom Cross tried to gather, he was beaten to the punch by Dave Yonwin who tapped into an empty net.
But Saints were back on level terms five minutes later when Manoochehri ran from his own half and rounded keeper Thomas McNulty to cap a superb solo effort.
With the interval approaching, Southam lost central defender Josh Turton, who was bleeding from a cut above the eye caused by a clash of heads.
With the injury requiring hospital treatment, Ben Tennant moved into the centre of defence, with Danny Wylde switching sides to left-back and Dan Rist taking his place on the right.
Swifts took the lead again in the 58th minute through Steven Day but it was all square in the 71st as Steve Thomas beat McNulty to a floated free-kick and the ball fell to Joe Williams, who fired into the net.
Then, Parsons, in only his second match, latched on to a short pass back to score the winner.
Tomorrow, Saints travel to Lichfield City before meeting Swifts again on Monday in the Birmingham County FA Midweek Floodlit Cup Final at Nuneaton Town FC (7.30pm).
To cap a busy week, they then face Racing Club Warwick at Banbury Road on Wednesday.
Saints are looking to recruit new managers for their reserve and youth teams for next season.
Candidates can apply via the club website or direct to [email protected]