The International Bomber Command Centre is being built in Lincolnshire, which became known as Bomber County in the war because it had so many RAF bases.
The centre is due to open in 2016 but a memorial spire has already been erected at the site in Lincoln.
Organisers want to invite every veteran to the unveiling on 2 October.
They already have names of 900 veterans but believe there are more still to be identified.
Nicky Barr from the International Bomber Command Centre says they have made some new contacts.
"A lot of the veterans that we've now been able to invite weren't on any comprehensive database or squadron lists," she said.
"We've picked up thus far about 50 that come under that category. We suspect that there's probably, at an estimate, another 100 out there."
The spire stands higher than the Angel of North and will be surrounded by a "wall of names" recording the 55,573 men who lost their lives serving in Bomber Command.
Other elements of the centre will include an exhibition and education space called the Chadwick Centre, an amphitheatre and acres of landscaped gardens.
Anyone knowing of any Bomber Command veteran is urged to register their names by emailing events@internationalbcc.co.uk or writing to The IBCC, 13 Cherry Holt Road, Bourne, Lincolnshire, PE10 9LA.

Edmund backed up two wins in qualifying with a 6-3 6-2 victory over world number 73 Garcia-Lopez in Beijing.
The 21-year-old from Yorkshire, ranked 54th, goes on to face another Spaniard, Roberto Bautista Agut, who beat John Millman 6-4 3-6 6-3.
Fellow Britons Andy Murray and Johanna Konta are in action on Tuesday.
Second seed Murray will play Italian Andreas Seppi in his opening match, while Konta takes on Hungary's Timea Babos as the British number one looks to maintain her hopes of a place at the season-ending WTA Finals.
American Madison keys, currently three places ahead of Konta in the eighth and final qualifying position, beat Kristina Mladenovic of France 7-5 6-4 on Monday.
There was an upset as China's unseeded Shuai Peng beat American sixth seed Venus Williams 7-5 6-1.
Every living veteran who served in Bomber Command during World War Two is being sought for the unveiling of a new memorial.
[NEXT_CONCEPT]
Britain's Kyle Edmund is through to the second round of the China Open following a straight-sets win over Spain's Guillermo Garcia-Lopez.