I believe that ANY 7-speed Shimano shifter can be used for with their 7-speed derailleurs ...
You can ALSO substitute a set of 8-speed Shimano shifters if they are more readily available and/or less expensive since the indexing is essentially the same.
Of course, a set of NEW shifters will typically cost less on eBay (<$30?) than from anywhere else unless you have a friend how will give you a free set.
If you need help with the installation, the information should be readily available on YouTube ... also, check www.parktool.com & www.sheldonbrown.com.
BTW. You many not need to buy a new set of shifters ...
Many of Shimano's MTB shifters can be opened up (they often have to be opened up to replace the cables) ... take the tension off the cable, clean & lube the mechanism with some light grease ("vaselline" will do) AND ensure that the teeth are not worn. It's a 15 minute "test" which may get you on the road which will also save you some coin.
BTW2. Because your bike has not been used for several years, you may want to ensure that your rear derailleur pivots freely when you press on them directly with your hand ... if not, then add a drop of 3-in-1 (or, equivalent) oil on the pivots ... wait 24 hours ... test ... repeat as necessary ...
That is, rust happens ... and, there is more steel on less expensive Shimano derailleurs which can be affected by rusting than will typically occur with their expensive derailleurs.
