The 19-year-old was killed when his motorbike crashed with a car outside a US military base in Northamptonshire on August 27 last year.
The car was allegedly driven by Anne Saccolas, the wife of an intelligence official based at RAF Croughton.
The 42-year-old claimed diplomatic immunity and was able to return to her home country, sparking an international controversy.
Harry’s mother Charlotte Charles and father Tim Dunn have both told ITV News of the emotional impact the coronavirus lockdown has had on them.
Ms Charles said with no particular focus each day and no particular plan to wake up to, "it hounds you a lot more".
"Being at home, being in his home environment, you can't leave that.
"Although I like my visuals, I have got his motorcycle jacket still in the kitchen and his toothbrush still in the bathroom, without lockdown, you're not able to get away from that, or try to avert your attention," Ms Charles told ITV News.
She said every day has been difficult "since we lost Harry in August".
Mr Dunn is currently helping out as a volunteer delivering food and medicines after being furloughed but added that he still reminisces about his son.
He told ITV News: "I've been finding myself looking more at pictures of Harry, thinking about him a lot more as I have time on my hands.
"Looking at videos, even finding myself talking to him...talking to him about how things are going or talking to him about football, just silly stuff, or looking at photos or videos."
ITV News recently learned the Foreign Office failed to tell police Ms Sacoolas was leaving UK.
A Foreign Office official said there was "not much mileage" in keeping Harry's alleged killer and her family in the UK just three weeks after his death.
Ms Charles said she can never trust Foreign Secretary Dominic Raab again after the claims emerged and said he should "re-evaluate the position he holds".
"We must get the truth for Harry's sake, he was a good lad and he deserves it," Mr Dunn said.
Ms Sacoolas was charged with causing Mr Dunn’s death by dangerous driving in December, but US Secretary of State Mike Pompeo rejected an extradition request at the start of the year.
The US State Department said the request would render the invocation of diplomatic immunity a practical nullity and would set an extraordinarily troubling precedent.
The prime minister, the foreign secretary and the home secretary have all labelled the extradition refusal a "denial of justice".
But Ms Charles and Mr Dunn said earlier this year that they had seen "no evidence" of the government reviewing its options after the extradition request for Ms Sacoolas was refused.
Ms Charles also questioned the leadership of Boris Johnson and a lack of action in bringing her son’s alleged killer back to the UK.
She said she felt as if her family had to drag the government "through a hedgerow backwards" to take steps to achieve justice for the teenager.
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