Speak to the pastor, vicar, priest or celebrant - get them to ask the congreation - there may be a carpenter, cabinet maker or experienced handyman who can see to it - let God provide a solution...
Alternatively...
If the lectern has a finish on it of wax or varnish it will not "take" stain. If varnished you might consider buying some coloured varnish to darken it. Gloss varnish leaves hideous reflections that show up any imperfections and a good tip is to finish with a coat of clear matt varnish to create a more pleasing sheen.
If the lectern is "undressed" then it will probably take wood stain and DIY stores, timber yard shops and hardware stores sell spirit based stains in a variety of colours (colors) and they'll sell beading too. Any beading or mouldings you fit may react differently to staining than will the body of the lectern - a trial application might be wise before applying the decorative pieces.
To find a wooden cross to apply to it use Google Images and enter "Carved Cross" for over 6000 results...
Good luck...
Peccavi
August 2009